Planetary boundary layer over Berlin at night

When we were ascending to 10,000 feet for light pollution measurements
on the evening of September 20, 2011, Ralf Steikert snapped this photo
of the "light smog" that seemed to float over the city. This
phenomena occurs because light pollution is easily scattered off of
aerosols (suspended small particles) below the planetary boundary
layer, but not so easily scattered in the clean air above. The bright
light in the photo is Olympiastadion.
Click on the image to see the full size version.